1. Technical Field
The present disclosure relates to a recycling system of anode off gas, and more particularly, to a recycling system of anode off gas in which a distance is adjusted between a nozzle of an ejector and a purge flow path where gas is discharged from an anode, and some gas discharged from the anode is mixed with pure gas supplied from a fuel tank by suction force of the ejector to be recycled to the stack.
2. Description of the Related Art
In general, a fuel cell system includes a fuel cell stack generating electrical energy, a fuel supply system supplying fuel (hydrogen) to the fuel cell stack, an air supply system supplying oxygen, that is, an oxidizer which is necessary for an electrochemical reaction, and a heat and water control system controlling an operating temperature of the fuel cell stack.
The fuel supply system, namely, a hydrogen tank of a hydrogen supply system stores high-pressure compressed hydrogen of about 700 bar. After the stored compressed hydrogen is discharged through a high-pressure line according to an on/off state of a high-pressure controller mounted at an inlet of the hydrogen tank, the compressed hydrogen is decompressed through a starting valve and a hydrogen supply valve to supply the fuel cell stack.
After hydrogen supplied to the stack performs a reaction for generation of electricity, some hydrogen is recycled to an anode and the remaining hydrogen is discharged via a purge valve, namely, a hydrogen purge is performed. When purging hydrogen, some hydrogen discharged from the stack is recycled to the anode of the stack and the remaining hydrogen is discharged through the purge valve.
Further, periodic purge of the anode of the fuel cell stack is performed to discharge nitrogen or water accumulated at the anode. Namely, since nitrogen and water accumulated at the anode of the stack cause performance of the stack to be deteriorated during operation of the fuel cell stack in a fuel cell vehicle, concentration of hydrogen is maintained at a certain level or more by periodic purge of the anode to secure stable performance of the stack.
Upon purging, the purging amount depends on a pressure difference between pressure of a hydrogen outlet and pressure of an air outlet, and an open time of a valve. Further, as output of the fuel cell system is increased, the amount of supplied air and hydrogen is increased to purge large amounts of anode off gas during opening of the purge valve in a high-output case as compared to a low-output case.
In a conventional configuration for recycling and purging hydrogen, as shown in FIGS. 1 and 2 (RELATED ART), a purge valve is disposed at a lower end of a stack manifold. Namely, a distance between an ejector and a purge flow path is large. As the distance therebetween increases, excess anode off gas is unnecessarily purged in the case of high output, thereby decreasing fuel efficiency.